Alternating phase mask

Abstract

An alternating phase mask having a branched structure containing two opaque segments is described. Two transparent surface segments are disposed on both sides of the segments or the components thereof, respectively. The surface segments are provided with phases that are displaced by 180°±Δ α, whereby Δ α a is not more than 25°. The surface segments are separated by at least one transparent surface boundary segment whose phase is situated between the phases of the adjacent surface segments.

We claim:  
     
       1. An alternating phase mask for exposing a photosensitive layer in a photolithographic process, the alternating phase mask comprising: 
       at least two opaque segments including a first opaque segment with a longitudinal side and a second opaque segment ending at the longitudinal side of the first opaque segment, the second opaque segment subdividing the first opaque segment into two opaque partial segments on either side of an end region of the second opaque segment;  
       transparent surface segments, one of the transparent surface segments disposed on each side of each of the two opaque partial segments and of the second opaque segment and extending over an entire length of the opaque segments, mutually adjacent ones of the transparent surface segments in each case having phases displaced by 180°±Δ α with respect to each other, and Δ α being at most 25°; and  
       a surface boundary segment disposed between two of the transparent surface segments and having a phase situated between the phases of the two of the transparent surface segments, the transparent surface segments separated by the surface boundary segment and situated opposite of the longitudinal side of the first opaque segment having the phases displaced by 180°±Δ α with respect to each other, the  
       surface boundary segment having a shape of an elongated rectangle with a width being substantially equivalent to a width of the second opaque segment.  
     
     
       2. The alternating phase mask according to  claim 1 , wherein the two opaque segments complement one another and form a T-shaped structure. 
     
     
       3. The alternating phase mask according to  claim 2 , wherein the T-shaped structure has a magnitude G where G=0.3·λ/NA, λ being a wavelength of radiation used in an exposure, and NA being a numerical aperture of an imaging system used for the exposure. 
     
     
       4. The alternating phase mask according to  claim 3 , wherein the two opaque segments each have a shape of an elongated rectangle. 
     
     
       5. The alternating phase mask according to  claim 2 , wherein the first opaque segment at a side opposite the end region of the second opaque segment has an indentation formed therein extending over a width of the end region. 
     
     
       6. The alternating phase mask according to  claim 2 , wherein the transparent surface segments have a rectangular cross-section. 
     
     
       7. The alternating phase mask according to  claim 6 , wherein the transparent surface elements have lengths corresponding in each case to lengths of adjacent ones of the two partial opaque segments. 
     
     
       8. The alternating phase mask according to  claim 1 , wherein the two opaque segments are chrome webs. 
     
     
       9. The alternating phase mask according to  claim 1 , wherein the Δ α=0 °. 
     
     
       10. The alternating phase mask according to  claim 9 , wherein the phases of the transparent surface segments are selected from the group consisting of 0° and 180°. 
     
     
       11. The alternating phase mask according to  claim 10 , wherein the phase of the surface boundary segment is 90°. 
     
     
       12. The alternating phase mask according to  claim 9 , wherein the phases of the transparent surface segments are selected from the group consisting of 90° and 270°. 
     
     
       13. The alternating phase mask according to  claim 12 , wherein the phase of the surface boundary segment is 0°. 
     
     
       14. The alternating phase mask according to  claim 1 , wherein the surface boundary segment transverse to boundary surfaces of adjacent ones of the transparent surface segments is divided up into partial segments having different phases. 
     
     
       15. The alternating phase mask according to  claim 1 , wherein the surface boundary segment has a homogeneous phase. 
     
     
       16. The alternating phase mask according to  claim 1 , wherein the surface boundary segment has a length adapted to lengths of adjacent ones of the transparent surface segments.